Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$201.89	6.851%	$215.7215	$215.72	$215.70	$215.70
Purchase #2	$165.49	10.168%	$182.317	$182.32	$182.30	$182.30
Purchase #3	$112.96	4.649%	$118.2115	$118.21	$118.20	$118.20
Purchase #4	$164.56	6.376%	$175.0523	$175.05	$175.05	$175.10
Purchase #5	$229.86	12.872%	$259.4476	$259.45	$259.45	$259.40
Purchase #6	$202.88	8.392%	$219.9057	$219.91	$219.90	$219.90
Purchase #7	$103.75	7.464%	$111.4939	$111.49	$111.50	$111.50
7 purchase totals =	$1,181.39		$1,282.1495	$1,282.15	$1,282.10	$1,282.10